Joint and Distinct Cognitive-Motor Associations with Multivariate White Matter Microstructure and Connectivity

Recent advances in cognitive neuroscience emphasise the importance of healthy white matter (WM) for optimal behavioural functioning. It is now widely accepted that brain connectivity via WM contributes to the emergence of behaviour. However, the association between the microstructure of WM fibres and behaviour is poorly understood due to the indirect and overlapping nature of methods used to assess microstructure. Here, we used the Mahalanobis Distance (D2) to integrate 10 metrics of WM derived from multimodal neuroimaging that have strong ties to microstructure. The D2 metric was chosen because it accounts for metrics' covariance as it measures the voxelwise distance between every subject and the average; thus providing a robust multiparametric assessment of microstructure. We used multivariate correlation to examine voxelwise WM-behaviour associations with two cognitive and two motor tasks, which allowed us to compare within and across behavioural domains. We observed that behaviour is organised in cognitive, motor, and integrative components that have widespread associations with WM, from frontal to parietal regions. Notably, the decomposition of these factors shows that tasks traditionally labelled as cognitive also contain motor components that map onto motor-related WM patterns, and that motor tasks likewise contain non-motor components linked to distinct WM microstructural features. Our results highlight the complex nature of the links between microstructure and behaviour, and support the relevance of multivariate modelling when examining brain-behaviour associations.